Page 20 - Air and Gas Drilling Manual

xxi List of Symbols
ν sr
2
ft /sec
2
= kinematic viscosity of he incompressible fluid, ft /sec
ν w = average kinematic viscosity at the exit end of the surface return flow line,
2
ρ g = density of the gas, lb-sec /ft 4
2
ρ gi = density of gas entering the drill string, lb-sec /ft 4
2
4
3
ρ m = drilling mud density, lb-sec /ft (slugs/ft )
ρ mixbh = density of the stable foam at eh bottomhole pressure and temperature, lb-
2
sec /ft 4
2
ρ sfa = density of foam exiting the case annulus and starts into the Tee, lb-sec /ft 4
2
ρ sfake = density of foam in the annulus, lb-sec /ft 4
2
ρ sfbp = density of foam upstream of the back pressure valve, lb-sec /ft 4
2
ρ w = density of incompressible fluid, lb-sec /ft 4
τ p = period of a single cycle of the piston, sec